title: Radiotracers binding to estrogen receptors: I: Tissue distribution of 17 alpha-ethynylestradiol and moxestrol in normal and tumor-bearing rats.
abstract: Ethynylestradiol and moxestrol can be labeled with carbon-11 by introducing this positron emitter in the 17 alpha-ethynyl group. To investigate their potential as radiotracers binding to estrogen receptors, we studied the tissue distribution of tritiated ethynylestradiol and moxestrol, with specific activities of 57 Ci/mmol and 77-90 Ci/mmol, respectively, in the adult female rat. At 30 min after injection, both compounds showed specific uptake in the uterus (% dose/g): 2.52 for ethynylestradiol and of 2.43 for moxestrol. A decrease of the specific activity to 6-9 Ci/mmol resulted in uterine uptakes of 1.60 and 2.10 respectively, for ethynylestradiol and moxestrol, at 30 min. In the female rat bearing DMBA-induced mammary tumors, specific uptake was also measured in the tumors, although the values were only 25-30% of the uterine uptake. Moxestrol showed a greater uptake selectivity in the tumors compared with ethynylestradiol. From this study we conclude that ethynylestradiol and moxestrol have good potential as tracers binding to mammary tumors that contain estrogen receptors.
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene; D000818:Animals; D002250:Carbon Radioisotopes; D045166:Estradiol Congeners / Q000378:metabolism*; D004971:Estrus; D004997:Ethinyl Estradiol / Q000031:analogs & derivatives* / Q000378:metabolism*; D005260:Female; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D011960:Receptors, Estrogen / Q000378:metabolism*; D014018:Tissue Distribution; D014599:Uterus / Q000378:metabolism
chemical_list: D002250:Carbon Radioisotopes; D045166:Estradiol Congeners; D011960:Receptors, Estrogen; D004997:Ethinyl Estradiol; D015127:9,10-Dimethyl-1,2-benzanthracene; C011310:moxestrol